The invention relates to valves for use in wellbores.
After a wellbore is drilled, various completion operations are performed to enable production of well fluids. Examples of such completion operations include the installation of casing, production tubing, and various packers to define zones in the wellbore. Also, a perforating string is lowered into the wellbore and fired to create perforations in the surrounding casing and to extend perforations into the surrounding formation.
To further enhance the productivity of a formation, fracturing may be performed. Typically, fracturing fluid is pumped into the wellbore to fracture the formation so that fluid flow conductivity in the formation is improved to provide enhanced fluid flow into the wellbore.
A typical fracturing string includes an assembly carried by coiled tubing, with the assembly including a straddle packer tool having sealing elements to define a sealed interval into which fracturing fluids can be pumped for communication with the surrounding formation. The fracturing fluid is pumped down the coiled tubing and through one or more ports in the straddle packer tool into the sealed interval.
After the fracturing operation has been completed, clean-up of the wellbore and coiled tubing is performed by pumping fluids down an annulus region between the coiled tubing and casing. The annulus fluids push debris (including fracturing proppants) and slurry present in the interval adjacent the fractured formation and in the coiled tubing back out to the well surface. This clean-up operation is time consuming and is expensive in terms of labor and the time that a wellbore remains inoperational. By not having to dispose of slurry, returns to surface are avoided along with their complicated handling issues. More importantly, when pumping down the annulus between coiled tubing and the wellbore, the zones above the treatment zone can be damaged by this clean-out operation. Further, under-pressured zones above the straddled zone can absorb large quantities of fluids. Such losses may require large volumes of additional fluid to be kept at surface for the sole purpose of clean-up.
An improved method and apparatus is thus needed for performing clean-up after a fracturing operation.
In general, in accordance with an embodiment, a tool for use in a wellbore comprises a flow conduit through which fluid flow can occur and a valve assembly adapted to be actuated between an open and closed position in response to fluid flow at greater than a predetermined rate.
Other features and embodiments will become apparent from the following description, from the drawings, and from the claims.